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| Titel |
Threshold values and management options for nutrients in a catchment of a temperate estuary with poor ecological status |
| VerfasserIn |
K. Hinsby, S. Markager, Brian Kronvang, J. Windolf, T. O. Sonnenborg, L. Thorling |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 16, no. 8 ; Nr. 16, no. 8 (2012-08-13), S.2663-2683 |
| Datensatznummer |
250013419
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| Publikation (Nr.) |
 copernicus.org/hess-16-2663-2012.pdf |
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| Zusammenfassung |
| Intensive farming has severe impacts on the chemical status of groundwater
and streams and consequently on the ecological status of dependent
ecosystems. Eutrophication is a widespread problem in lakes and marine
waters. Common problems are hypoxia, algal blooms, fish kills, and loss of
water clarity, underwater vegetation, biodiversity and recreational value.
In this paper we evaluate the nitrogen (N) and phosphorus (P) concentrations
of groundwater and surface water in a coastal catchment, the loadings and
sources of N and P, and their effect on the ecological status of an estuary.
We calculate the necessary reductions in N and P loadings to the estuary for
obtaining a good ecological status, which we define based on the number of
days with N and P limitation, and the corresponding stream and groundwater
threshold values assuming two different management options. The calculations
are performed by the combined use of empirical models and a physically based
3-D integrated hydrological model of the whole catchment. The assessment of
the ecological status indicates that the N and P loads to the investigated
estuary should be reduced to levels corresponding to 52 and 56% of the
current loads, respectively, to restore good ecological status. Model
estimates show that threshold total N (TN) concentrations should be in the range
of 2.9 to 3.1 mg l−1 in inlet freshwater (streams) to Horsens estuary
and 6.0 to 9.3 mg l−1 in shallow aerobic groundwater (∼ 27–41 mg l−1
of nitrate), depending on the management measures
implemented in the catchment. The situation for total P (TP) is more complex, but
data indicate that groundwater threshold values are not needed. The stream
threshold value for TP to Horsens estuary for the selected management
options is 0.084 mg l−1. Regional climate models project increasing
winter precipitation and runoff in the investigated region resulting in
increasing runoff and nutrient loads to the Horsens estuary and many other
coastal waters if present land use and farming practices continue. Hence,
lower threshold values are required in many coastal catchments in the future
to ensure good status of water bodies and ecosystems. |
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